This section provides background information related to the present disclosure which is not necessarily prior art.
Various pressure relief devices are used to vent a pressurized substance, such as a gas, when activated under specified performance conditions. For example, such pressure relief devices can be used to vent the contents of a compressed hydrogen fuel container. The pressure relief device can be designed to achieve a desired flow capacity for protection of the hydrogen fuel container so the container is fully vented in a particular amount of time.
Certain high pressure containers can be classified into four types: a Type I vessel having an all-metal construction; a Type II having a metal lined construction with a fiberglass hoop wrap; a Type III having a metal lined construction with a composite full wrap; and a Type IV having a plastic lined construction with a composite full wrap. Such high pressure vessels for containing a compressed hydrogen gas should provide the necessary mechanical stability and integrity to prevent rupture or bursting of the pressure vessel from the hydrogen fuel pressure within. Pressure vessels for use in a vehicle can also be made using lightweight materials so they do not significantly affect the weight requirements of the vehicle. In some cases, the Type IV pressure vessel can be used for storing compressed hydrogen gas on a vehicle.
As described by Immel in U.S. Pat. No. 6,742,554, incorporated herein by reference in its entirety, the Type IV pressure vessel contemplated for storage of hydrogen gas is generally cylindrical in shape to provide the desired integrity, and includes an outer structural wall and an inner liner defining a container chamber therein. The combination of the outer wall and the liner provide the structural integrity, pressure containment, and gas tightness in a lightweight and cost effective manner.
Such pressure vessels can include an adapter that provides the inlet and outlet opening for the hydrogen gas contained therein. The adapter can house various valves, pressure regulators, piping connectors, excess flow limiter, etc. These components allow the pressure vessel to be filled with the compressed hydrogen gas and allow the compressed gas to be discharged from the pressure vessel at or near ambient pressure, or a higher pressure, and be sent to a user of the gas, such as a fuel cell power plant. The adapter can be made of steel, for example, to provide structural strength for storing the compressed hydrogen gas. A suitable adhesive, sealing ring, or the like can be employed to seal the liner to the adapter in a gas tight manner, and secure the adapter to the outer wall of the vessel.
Pressure vessels for use as fuel containers can have internal process faults or can be exposed to external elevated temperatures. Such conditions may act to increase the contained pressure and/or to degrade the structural materials, depending on the container type and construction. Incorporation of a pressure relief device provides a means to vent the fuel container under such conditions. In some pressure vessels, the pressure relief device can be located at the adapter or opening of the pressure vessel.
One type of pressure relief device is a Thermally-activated Pressure Relief Device (TPRD) that is activated by elevated temperature. The TPRD can be located in the same area or compartment as the fuel container or systems that are being protected so that it is exposed to the same environment. In this manner, the TPRD can react to the same conditions experienced by the fuel container. Shields and flow barriers, if any, can be positioned so they do not interfere with the response and functionality of the TPRD.
Various TPRDs exhibit limitations in certain applications. For example, one issue with glass bulb TPRD designs can be a loss of release piston movability during service-life. Corrosion and/or foreign material can block or freeze the release piston and hinder the activation function, where the piston is required to move and release the pressurized material. A loss of release piston movement can occur without any notice or indication. Moreover, once the TPRD is installed, there may be no way to check and ensure the release piston is not seized during the TPRD lifetime. In many cases, activation testing is not possible.